Intraluminal medical device having improved visibility

ABSTRACT

A stent may be formed of at least one structural material having a pattern including at least one serpentine structure which extends about the longitudinal axis of the stent. The structure is formed of a plurality of struts. Adjacent struts are interconnected by end portions having inner turns and outer turns. At least some of the end portions are elongated and other end portions are non-elongated and have a predetermined length. The inner turns of the elongated end portions are substantially unaligned longitudinally with the inner turns of the non-elongated end portions. At least one of said elongated end portions is configured to serve as a fiducial marker.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a Continuation of Ser. No. 10/269,112, now U.S. Pat.No. 7,331,986, filed Oct. 9, 2002, the entire content of which isincorporated by reference herein.

BACKGROUND OF THE INVENTION

Stents are generally tubular shaped devices that function to hold open asegment of a blood vessel or other anatomical lumen and are useful inthe treatment of atherosclerotic stenoses in blood vessels. Stents areparticularly suitable for use in supporting and holding back a dissectedarterial lining that can occlude the fluid passageway therethrough.

Stents are available in a variety of configurations, includingself-expanding and mechanical expanding varieties, but regardless of theconfiguration, are typically delivered to the site of theatherosclerotic stenosis through the use of a catheter delivery device.

To accomplish precise placement of stents, various means are employedfor identifying the position of the stent within a blood vessel. As thestents themselves are typically formed of a metal, metal alloy orpolymeric material which is not readily visible using known techniquesfor viewing the stent such as fluoroscopy or MRI, such characteristicsmust be imparted to the stent structure. One method is to impartradiopacity to the stent structure such as by attachment of markers tothe stent structure, or by making the entire stent from a radiopaquematerial, so that, through the use of fluoroscopy, the position of thestent within a blood vessel can be identified. Once the stent with itsradiopaque markers has been implanted, identification of the stentposition during subsequent checkups of the treated segment is easilyaccomplished because the markers remain visible under fluoroscopy.Another method is to provide stent materials which are visible usingMRI.

Stents are most commonly formed of materials which have littleradiopacity such as stainless steel or shape memory metal alloys such asNITINOL® which is a nickel-titanium shape memory alloy, for example. Forone, making the entire stent out of a radiopaque material can be quitecostly. Another disadvantage is that the stent may fluoresce toobrightly which may actually make it more difficult for the physician toaccurately position the stent, as well as to make follow up checks onthe functioning of the stent more difficult.

There have been several methods employed for attaching radiopaquemarkers to a stent. One method has been to coat the deformable portionsof the stent with radiopaque material. This can require a relativelythick coating in order to provide enough radiopaque material to bevisible using fluoroscopy, and can also alter the mechanical performanceof the stent.

Another method has been to insert radiopaque material into a hollowstent wire.

Other methods of attaching radiopaque markers have been employed such asthat described in U.S. Pat. No. 6,334,871 in which radiopaque markersdescribed therein as rivets are inserted into openings in the stent.

There remains a need in the art for improved stents as well as otherimproved intraluminal medical devices which are easily and readilyvisualized in the vasculature of a patient for accurate placement andfor accurate future detection in the desired body lumen, and to improvedmethods of making the same.

All U.S. patents and applications and all other published documentsmentioned anywhere in this application are incorporated herein byreference in their entirety.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a partial view of a stent according to the present inventionhaving elongated end portions.

FIG. 2 is a partial view of an alternative embodiment of a stentaccording to the present invention having elongated and enlarged endportions.

FIG. 3 is a partial view of an alternative embodiment of a stentaccording to the present invention having end portions designed foraccepting fiducial markers for enhancing visibility.

FIG. 4 is a partial view of an alternative embodiment of a stentaccording to the present invention in which the end portions include avoid for inserting fiducial markers.

FIG. 5 is a partial view of an alternative embodiment of a stent similarto that shown in FIG. 4 wherein the end portions have alternative voidsfor inserting fiducial markers.

FIG. 6 is a flat pattern of a stent according to the present inventionwherein the stent exhibits two elongated end portions interspersed witha non-elongated end portion.

FIG. 6 a is an exploded partial view of the same stent as shown in FIG.6.

FIG. 7 is a flat pattern of a stent according to the present inventionwherein the stent exhibits two non-elongated end portions separated byone elongated end portion.

FIG. 7 a is an exploded partial view of the same stent as shown in FIG.7.

FIG. 8 is a schematic of a spiral embodiment of the stent.

SUMMARY OF THE INVENTION

The present invention relates to intraluminal medical devices, includingstents and stent grafts having fiducial markers to enhance visibility ofthe device in the vasculature of a patient both during the delivery andplacement of the device, and for future observation of the device duringfollow up visits.

In general, the stents of the present invention are tubular structuresformed of a serpentine structure that typically includes at least oneserpentine band and desirably a plurality of serpentine bands which areinterconnected by connecting members between adjacent serpentine bands.The serpentine bands may be in the form of circumferential bands orbands which spiral about the longitudinal axis of the stent. Theserpentine bands are formed of a plurality of struts, adjacent ones ofwhich are connected by alternating end portions. The end portions haveinner turns and outer turns. Some of the end portions in the stentcircular band pattern are elongated and are configured so as to provideenhanced visibility of that portion of the stent structure. Theelongated end portions do not extend substantially beyond thenon-elongated end portions, however. The outer turns of the elongatedportions do not have to align longitudinally with the outer turns of thenon-elongated portions, and the inner turns of the elongated portions donot have to align longitudinally with the inner turns of thenon-elongated portions.

In some embodiments, the enhanced visibility is provided by havingelongated end portions with increased mass. The elongated end portionsmay also be enlarged in addition to being elongated. The elongated endportions with higher mass are preferentially configured such that theelongated end portions do not extend substantially longitudinally beyondthe other non-elongated end portions of the band.

In one embodiment, the end portion includes an extension whichincorporates a fiducial marker. In this embodiment, the overall lengthof the extension and the end portion, does not extend substantiallybeyond the length of the other end portions which are neither elongated,nor have any extensions. In this embodiment the outer turns of the endportions having the extension do not have to longitudinally align withthe outer turns of the other end portions, and the inner turns of theend portions having the extensions do not have to longitudinally alignwith the inner turns of the other end portions.

In another embodiment, the elongated end portions may be adapted toreceive a fiducial marker such as a plug, rivet, wire winding, band,filling, coating or the like.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

While this invention may be embodied in many different forms, there aredescribed in detail herein specific embodiments of the invention. Thisdescription is an exemplification of the principles of the invention andis not intended to limit the invention to the particular embodimentsillustrated.

For the purposes of this disclosure, unless otherwise indicated,identical reference numerals used in different figures refer to the samecomponent.

Structures which are in longitudinal alignment or which are alignedlongitudinally, for the purposes of this disclosure, are structure whichare at the same axial position along the longitudinal axis of the stentbut which may be located apart from one another about the circumferenceof the stent. Thus, for example, in the stents of FIGS. 6 and 7,proximal-most outer turns 20 a and 20 b are substantially longitudinallyaligned with one another and distal-most outer turns 20 a and 20 b aresubstantially longitudinally aligned with one another.

In general, the stents of the present invention are tubular structuresformed of a serpentine structure that typically includes at least oneand desirably a plurality of serpentine bands. The serpentine bands maybe circumferential bands or may spiral about the longitudinal axis ofthe stent. Each serpentine band is formed of a plurality of struts whichare interconnected by end portions, each end portion having an innerturn and an outer turn. Where a plurality of serpentine bands arepresent, the serpentine bands are also interconnected by connectingelements. Some of the end portions of the stent structures of thepresent invention are adapted to provide enhanced visibility usingimaging techniques such as fluoroscopy or magnetic resonance imaging(MRI) by providing elongated or extended end portions of sufficient areaor mass which can serve as fiducial markers themselves or in conjunctionwith at least a second material provided in the region of the elongatedor extended end portion.

As used herein, the term “fiducial marker” shall be used to includethose portions of the stent which have properties which make them havelocally enhanced visibility in the imaging modality which will be usedto acquire an image of the patient's body. For example, where x-raybased imaging modalities will be used, the fiducial markers are ofincreased area or mass and/or of more radiopaque material. If magneticresonance imaging is employed, the fiducial markers have magneticresonance properties which are different from the magnetic resonanceproperties of the remainder of the stent.

Turning now to the figures, FIG. 1 is a partial view of a stent 10formed of a plurality of circumferential bands 12 which areinterconnected by connecting elements 22. The connecting elements 22shown in this and the following figures are shown as straight connectingelements. However, other variations may be employed including, forexample, curved, bent, linear, curvilinear, and so forth. Shown in FIG.1 is a single circumferential band 12 but the connecting elements 22 tothe next circumferential band are visible. Band 12 is formed of aplurality of struts interconnected by end portions 16 a, 16 b, each endportion having an inner turn 18 a, 18 b and an outer turn 20 a, 20 b.Some of the end portions 16 b of each circumferential band are designedto exhibit enhanced visibility, desirably by providing enhancedradiopacity when using fluoroscopic techniques, or by providingdifferent MRI properties when using MRI. In this particular embodiment,the end portions 16 b have an elongated structure for providingincreased mass and enhanced radiopacity.

In this embodiment, not all of the turns of the end portions need besubstantially longitudinally aligned with one another. However, theelongated end portions 16 b have outer turns 20 b, which do not extendsubstantially beyond the outer turns 20 a of any of the othernon-elongated end portions 16 a. Further, the inner turns, 18 b, of theelongated end portions 16 b, are not substantially longitudinallyaligned with the inner turns 18 a of the non-elongated end portions 16a.

FIG. 2 shows generally at 10, a partial view of another embodiment of astent structure according to the present invention. In this embodiment,the overall structure is substantially similar to that of FIG. 1, but,the end portions 16 b, are not only elongated, but are further enlargedas well. Again, none of the outer turns 20 b, of the elongated, enlargedend portions 16 b, extend longitudinally substantially beyond the endportions of 16 a. The inner turns 18 b of the elongated and enlarged endportions 16 b, are not substantially longitudinally aligned with theinner turns 18 a of the non-elongated end portions 16 a.

FIG. 3 is a partial view of yet another embodiment of a stent accordingto the present invention. In this embodiment, the end portions 16 b,have an extension 17 for attaching a fiducial marker such as a wirewinding, marker band, plating, coating and the like, for example. Theinner turns 18 b of the end portions 16 b having the extensions 17 donot longitudinally align with the inner turns 18 a of the end portions16 a which have no extensions. The outer turns 20 b of end portions 16 bwhich have extensions 17, are not substantially longitudinally alignedwith the outer turns 20 a of the other end portions 16 a which do nothave any extensions. The extensions 17 of the end portions 16 b, do not,however, extend substantially beyond the length of the end portions 16a. FIGS. 4 and 5 are illustrative of another embodiment of the stentstructure according to the present invention in which the elongated endportions are adapted for receiving some sort of fiducial marker such asa plug, rivet, filling, plating, coating and so forth.

FIG. 4 illustrates an embodiment of the present invention in which asubstantial portion of the elongated end portions 16 b is adapted with afitting 19 for accepting a visibility enhancing marker 21. Thecircumferential band as shown has a plurality of non-elongated endportions 16 a and a plurality of elongated end portions 16 b. Again, thelength of the elongated end portions 16 b does not extend substantiallybeyond the length of the non-elongated end portions 16 a. The outerturns 20 b of the elongated end portions 16 b are substantiallylongitudinally aligned with the outer turns 20 a of the non-elongatedend portions 16 a in this embodiment, but this is not a requirement. Theinner turns 18 b of the elongated end portions 16 b are notsubstantially longitudinally aligned with the inner turns 18 a of thenon-elongated end portions 16 a.

FIG. 5 illustrates an embodiment of the present invention which issubstantially similar to that shown in FIG. 4, with the exception thatthe fitting 17 for accepting the fiducial marker 19, is smaller, inrelation to the elongated end portion 16 b.

FIG. 6 shows a flat pattern of a stent 10 according to the presentinvention formed of a plurality of bands 12 interconnected by connectingelements 22. The actual stent is tubular. Band 12 is formed of aplurality of struts interconnected by end portions 16 a, 16 b, each endportion having an inner turn 18 a, 18 b and an outer turn 20 a, 20 b.Some of the end portions 16 b of each circumferential band are designedto exhibit enhanced visibility, desirably by providing enhancedradiopacity when using fluoroscopic techniques, or by providingdifferent MRI properties when using MRI. In this particular embodiment,the end portions 16 b have an elongated structure for providingincreased mass and enhanced radiopacity.

In the embodiment shown in FIG. 6, there are at least two adjacentelongated end portions 16 b separated by a non-elongated end portion 16a at one end of the stent and at least two adjacent non-elongated endportions 16 a separated by an elongated end portion 16 b at the otherend of the stent.

FIG. 6 a is an exploded view of a portion of the stent 10 shown in FIG.6 illustrating the elongated end portions 16 b. Variations may be madein the structure shown in FIGS. 6 and 6 a such as having more than twoadjacent elongated end portions 16 b, for example. Furthermore, whileconnecting elements 22 shown in FIGS. 6 and 6 a are straight, othervariations may be employed such as curved, bent, linear, curvilinear,and so forth.

FIG. 7 shows a flat pattern of an alternative embodiment of the stent 10according to the present invention formed of a plurality ofinterconnecting bands 12 interconnected by connecting elements 22. Theactual stent is tubular. Band 12 is formed of a plurality of strutsinterconnected by end portions 16 a, 16 b, each end portion having aninner turn 18 a, 18 b and an outer turn 20 a, 20 b. Some of the endportions 16 b of each circumferential band are designed to exhibitenhanced visibility, desirably by providing enhanced radiopacity whenusing fluoroscopic techniques, or by providing different MRI propertieswhen using MRI. In this particular embodiment, the end portions 16 bhave an elongated structure for providing increased mass and enhancedradiopacity.

In the embodiment shown in FIG. 7, there are two adjacent non-elongatedend portions 16 a separated by an elongated end portion 16 b at one endof the stent and there are two adjacent elongated end portions 16 bseparated by a non-elongated end portion 16 a at the other end of thestent. FIG. 7 a is an exploded view of a portion of the stent 10 shownin FIG. 7 illustrating the elongated end portions 16 b. Variations maybe made in the structure shown in FIGS. 7 and 7 a such as having morethan two adjacent non-elongated end portions 16 a, for example.Furthermore, while connecting elements 22 shown in FIGS. 6 and 6 a arestraight, other variations may be employed such as curved, bent, linear,curvilinear, and so forth.

In accordance with the invention, a stent may comprise a single bandsuch as that shown in FIGS. 1-7 a or a plurality of such bands.

The inventive stents may also be provided in other configurations aswell. For example, any of the inventive stents disclosed herein may alsobe provided in spiral embodiments in which the serpentine bands orcellular structures spiral about the longitudinal axis of the stent. Anexample of such a configuration is shown schematically in a flat patternin FIG. 8. Some of the peaks 16 b at the end of the stent are providedwith elongated end portions to serve as fiducial markers and some of thepeaks 16 a do not have elongated end portions.

Any of the inventive stents disclosed herein may also be provided in a‘jelly roll’ configuration. For example, the flat pattern of FIG. 7 maybe rolled into a tube without securing the longitudinal edges to oneanother. Such a stent would be deployed by unrolling of the stent andexpansion of the cells or bands which extend about the longitudinal axisof the stent. An example of such a stent is disclosed in WO0132099.

The stents according to the present invention are formed of at least onebase material hereinafter referred to as the structural material. Anysuitable material known in the art for forming such intraluminal medicaldevices may be employed including both metallic materials and polymericmaterials, although metallic materials are preferred.

Examples of suitable metallic materials include, but are not limited tostainless steel, and shape memory alloys. Examples of such materialsinclude, but are not limited to, NITINOL® which is a nickel-titaniumalloy, cobalt-chromium alloys such as ELGILOY®, platinum-tungstenalloys, and so forth. Other alloys which may be employed in makingformation of the stent structure include, but are not limited to, cobaltchromium alloys, other alloys of titanium cobalt-chromium molybdenumalloys, and so forth.

The fiducial markers, as described above, enhance visibility of thestent in conjunction with an imaging modality such as, for example, MRIand fluoroscopy.

One way to provide regions of altered MR contrast in an intraluminalmedical device is to employ polymeric materials containing aparamagnetic ion. Examples of coatings which are suitable for enhancingthe visualization of desired regions of a stent are disclosed in U.S.Pat. No. 6,361,759, incorporated herein by reference. Ferromagneticmaterials such as iron, nickel, cobalt and alloys of these materials mayalso enhance the visualization of the desired regions of the stent.Paramagnetic materials including gadolinium and alloys and salts thereofmay also be used to alter the imaging characteristics of the stent.

Other compounds which may find utility herein and serve as keycomponents of various contrast agents for MRI include, but are notlimited to polychelating and amphiphilic polymers. Some examples ofpolychelating polymers are those having poly-L-lysine (PLL) as the mainchain and chelating moieties such as diethylene traimine pentaaceticacid or DTPA as side groups.

It may further be noted that some polymer surfaces may optionally becoated further with hydrophilic layers.

Materials which may be employed in the formation of the radiopaquemarker include, but are not limited to, the noble metals includingruthenium (Ru), rhodium (Rd), palladium (Pd), osmium (Os), iridium (Ir),platinum (Pt), silver (Ag), and gold (Au), tantalum (Ta), rhenium (Re),and so forth, molybdenum, iodine and its salts or compounds, barium andits salts or compounds, bismuth and its salts or compounds, tungsten,and so forth.

Polymeric materials which incorporate radiopaque materials such asbarium, may also be employed to form radiopaque marker materials.

In addition to the specific embodiments claimed below, the invention isalso directed to other embodiments having any other possible combinationof the dependent features claimed below. As such, the particularfeatures presented in the dependent claims can be combined with eachother in other manners within the scope of the invention such that theinvention should be recognized as also specifically directed to otherembodiments having any other possible combination of the features of thedependent claims. For instance, for purposes of claim publication, anydependent claim which follows should be taken as alternatively writtenin a multiple dependent form from all prior claims which possess allantecedents referenced in such dependent claim if such multipledependent format is an accepted format within the jurisdiction.

The above Examples and disclosure are intended to be illustrative andnot exhaustive. These examples and this description will suggest manyvariations and alternatives to one of ordinary skill in this art. Allthese alternatives and variations are intended to be included within thescope of the attached claims. Those familiar with the art may recognizeother equivalents to the specific embodiments described herein whichequivalents are also intended to be encompassed by the claims attachedhereto.

1. A stent formed of at least one structural material and having apattern including a plurality of serpentine structures comprising afirst end serpentine structure, a second end serpentine structure, andat least one intermediate serpentine structure therebetween, each endserpentine structure extending about the longitudinal axis of the stentand formed of a plurality of struts, adjacent struts interconnected byend portions having inner turns and outer turns, the inner turns andouter turns and struts therebetween forming a series of peaks andtroughs, the outer turns of the peaks of the end serpentine band definean end of the stent; wherein the outer turns of troughs of the endserpentine band are connected to outer turns of an adjacent intermediateserpentine structure by connecting elements; wherein at least some ofthe end portions of the end serpentine structure are elongated and havea first predetermined length and other end portions are non-elongatedand have a second predetermined length, the first predetermined lengthgreater than the second predetermined length; wherein none of theelongated end portions are connected to the adjacent intermediateserpentine structure; wherein the inner turns of the elongated endportions are substantially unaligned longitudinally with the inner turnsof the non-elongated end portions and wherein at least one of saidelongated end portions is configured to serve as a fiducial marker. 2.The stent of claim 1, wherein said fiducial marker is of the samematerial as the remainder of the stent.
 3. The stent of claim 1, whereinsaid outer turns of said elongated end portions are substantiallylongitudinally aligned with said outer turns of said non-elongated endportions.
 4. The stent of claim 1 wherein said fiducial marker comprisesat least one material which is more radiopaque, or has different MRproperties, or both, than said structural material.
 5. The stent ofclaim 1 wherein said fiducial marker comprises at least one materialwhich is more radiopaque than said structural material said radiopaquematerial selected from the group consisting of ruthenium, rhodium,palladium, osmium, iridium, platinum, silver, gold, tantalum, rhenium,molybdenum, iodine and its salts or compounds, barium and its salts orcompounds, bismuth and its salts or compounds, tungsten, and mixturesthereof.
 6. The stent of claim 1 wherein at least some of the elongatedend portions are plated or coated with a radiopaque coating.